This invention relates to a general method for preparing homogeneous blends of poly(ethylene naphthalate) and other polyesters with poly(ether imide)s.
A novel blend of poly(ethylene naphthalate) (PEN) with poly(ether imide) (PEI) was disclosed in U.S. Pat. No. 5,599,658 as a resin formulation with a number of useful properties which makes it especially advantageous for use in photographic film. In particular, a film manufactured from this blend at a certain composition range generally retains the desirable properties of PEN film, while having a lower propensity to take up core-set curl. This property permits its use in small diameter cartridgesxe2x80x94for example, diameters in the range of -12.5 mmxe2x80x94without suffering the consequence of an increased curl in the wound film. It is also possible to use less extreme annealing conditions (lower annealing temperature and/or shorter annealing time) with a film comprising the said blend formulation to achieve equivalent core-set propensity to that of PEN film.
However, preparation of the blend formulation in accordance with U.S. Pat. No. 5,599,658, the contents of which are incorporated herein in their entirety, requires thorough drying of all components and an additional compounding step using, typically, a twin-screw extruder or equivalent melt compounding equipment. These additional steps raise the cost of the blend and make it less attractive economically compared to the unblended PEN resin. In addition, the need to heat the resin components to high temperature during compounding can lead to thermal and hydrolytic degradation as well as contamination of the blended resin with debris from the compounding equipment.
What is needed in the art is a method of preparing a blend of poly(ether imide) (PEI) with poly(ethylene naphthalate) (PEN), poly(ethylene terephthalate) (PET) and other polyesters that overcomes the problems noted above.
The present invention discloses an in-situ process of blending PEI and polyesters that provides better control of the blended polymer viscosity and avoids problems heretofore encountered in the blending process.
The conventional, high temperature compounding step can be eliminated by adding the PEI resin directly into the reactor used for preparing the PEN polymer. The invention discloses that, contrary to expectation, the presence of PEI pellets in the polyester polymerization reaction vessel has no adverse effect on the kinetics and extent of the polymerization reaction and allows easy blending and homogenizing of the added PEI resin with the polymerizing PEN species. The final resin obtained by this xe2x80x9cin-situxe2x80x9d blending process is a homogeneously dispersed PEN/PEI blend with a sufficiently high inherent viscosity (IV) and a single glass transition temperature (Tg).
Poly(ethylene naphthalene), sometimes abbreviated as PEN, previously has been used as a support for magnetic recording and playback tapes and had been proposed for use as a support for photographic film, for example in U.S. Pat. No. 4,141,735, U.S. Pat. No. 5,294,473 and U.S. Pat. No. 5,368,997. The ""473 and ""997 patents broadly describe copolyesters with PEN and blends of PEN with other polymers, but not with a poly(ether imide). The PEN used in the polymer blend of this invention can be the same polymer as described in this prior art, such as U.S. Pat. No. 5,368,997, the disclosure of which is incorporated herein by reference. Preferably it is PEN, particularly poly(ethylene-2,6-naphthalate).
The PEN used in the polymer blends of this invention preferably has molecular weights represented by inherent viscosities in the range of 0.5 to 0.9 dl/g. (Inherent viscosity is measured in a Ubbelhode capillary viscometer (Shott Gerate 536-13) at 25xc2x0 C. and at a polymer concentration of 0.25 g/dL in a 50/50 mixture by weight of pentafluorophenol and 1,2,4-trichlorobenzene.) The PEN used in the polymer blends of this invention preferably has a glass transition temperature (Tg), above about 118xc2x0 C.
Poly(ether imide), sometimes abbreviated as PEI, is the condensation product of a bis(etherdianhydride) and an organic diamine. Its synthesis, structure and use are described in U.S. Pat. Nos. 3,803,085, 3,847,867, 3,905,942, 4,011,198 and 4,293,684. The particular PEI used in the polymer blends of this invention can be as described in this prior art, such as U.S. Pat. No. 3,847,867, the disclosure of which is incorporated herein by reference. A preferred PEI is one in which the bis(etherdianhydride) is 2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl]propane dianhydride (also known as Bisphenol A dianhydride) and the organic diamine is m-phenylene diamine.
Preferably, the PEI has a molecular weight represented by a melt viscosity in the range of 103 to 105 poise. Melt viscosity is measured according to the following procedure: A sample of the PEI in pellet form is dried under vacuum at 150xc2x0 C. for 10 hrs. The dried sample is loaded into a parallel disk (25 mm diameter) fixture of a Rheometrics System IV(copyright) rheometer (manufactured by Rheometrics, Inc., Possumtown Rd., Piscataway, N.J. 08854) and its temperature is raised to 305xc2x0 C. The viscosity of the melt is determined by shearing the resin at a constant oscillating frequency of 1 rad/s.
The PEI used in this invention preferably has a glass transition temperature (Tg) which is above 150xc2x0 C. In addition, the PEI should be miscible with the PEN. By miscible is meant that the blend of the two polymers has a single glass transition temperature (Tg) and that a photographic film base made from the blend is clear. The PEI is available commercially from the General Electric Company, One Plastics Ave., Pittsfield, Mass. 01201, under the Ultem(copyright) trade name. Representative grades are Ultem 1000(copyright) and Ultem 1010(copyright).
Blending of PEI with polyesters, such as PET and PEN is broadly described in U.S. Pat. No. 4,141,927 and Research Disclosure, November 1987, Item 28338, pages 677-8. (Research Disclosure is published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire P010 7DQ, ENGLAND.) These patents and publication do not describe the blends of this invention or suggest that they would be suitable for use as a photographic film base. Nor does any of this art suggest that blending PEI with PEN would have any influence on the core-set and post-process curl characteristics of a film based prepared from the blend, let alone suggest that such a blend would provide a film base in which these characteristics were improved.
The blends of this invention preferably have the following physical characteristics: a Tg of greater than 125xc2x0 C.; a tensile modulus greater than 350 Kg/mm2; light transmission greater than 80%; and haze less than 3%. The way in which these characteristics are determined is described in the Examples in U.S. Pat. No. 5,599,658.
While the relative proportions of PEN and PEI may vary somewhat with variations in the particular PEI employed, as well as with the presence of other components in the blend, preferred proportions of PEN and PEI in the blends of this invention are from 70 to 95 weight percent PEN and from 5 to 30 weight percent of PEI. When the proportion of PEI is increased, we have found that the tensile modulus is decreased, the crystallinity of the blend is lowered and a sheet formed from the blend becomes difficult to stretch. When the proportion of PEI is decreased below the said range, we have found that the improvement in physical performance of the blend becomes insignificant. Preferably the proportion of PEI is between 10 and 20 percent by weight. Most preferably the proportion of PEI is between 12 and 17 percent by weight. These are the preferred proportions for PEI prepared from bisphenol A dianhydride and m-phenylene diamine.
Film base is prepared from the polymer blend by techniques known to those skilled in the art. These techniques are described in detail in Schrader U.S. Pat. No. 4,141,735, the disclosure of which is incorporated herein by reference. A film base is understood to be a planar sheet having a thickness in the range of 50 to 200 xcexcm, preferably a thickness of 70 to 110 xcexcm.
In a typical operation, the film base is formed by extruding the polymer blend at a temperature of 290 to 320xc2x0 C. through a sheeting die and casting the molten sheet on a chill roll at a temperature of 60 to 120xc2x0 C. The cast sheet is then stretched biaxially to from 2 to 5 times its initial lateral dimensions. tretching can be at a temperature in the range of from 130 to 170xc2x0 C. Biaxial stretching can be sequential or simultaneous. After stretching the film base is heatset at a temperature in the range of 200 to 250xc2x0 C. for time in the range of 0.1 to 10 sec. If the film base is to be annealed, it can be annealed at a temperature in the range of from 50xc2x0 C. up to the Tg of the polymer blend for a time in the range of 0.1 to 1000 hours. Film base with core-set characteristics useful for small diameter film cartridges can be obtained with preferred blends of this invention by annealing at temperatures of between about 90 and 125 xc2x0 C. for times of 6 to 72 hrs.
Film base prepared from polymer blends of this invention can contain other components commonly found in film supports for photographic elements. These include dyes, lubricants and particles of organic and inorganic materials such as glass beads. These are described in more detail in Research Disclosure, February 1995, Item 37038, pages 79-114.
Film base prepared from polymer blends of this invention can bear layers commonly found on film supports used for photographic elements. These include magnetic recording layers, subbing layers between other layers and the support, photosensitive layers, interlayers and overcoat layers, as are commonly found in photographic elements. These layers can be applied by techniques known in the art and described in the references cited in Research Disclosure Item 37038 cited above.
Magnetic recording layers that can be used in photographic elements of this invention are described in U.S. Pat. Nos. 3,782,947; 4,279,945; 5,147,768; 5,252,441; 5,254,449; 5,395,743; 5,397,826; 5,413,902; 5,427,900, 5,432,050, 5,434,037, 5,436,120, in Research Disclosure November 1992, Item 34390, pages 869 et seq.
Photographic elements of this invention can have the structures and components shown on Research Disclosure 37038 cited above and can be imagewise exposed and processed using known techniques and compositions, including those described in the Research Disclosure Item 37038 cited above.
Blending of PEI with polyesters, such as PET and PEN, is broadly described in U.S. Pat. No. 4,141,927 and Research Disclosure, November 1987, Item 28338, pages 677-8 (Research Disclosure is published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire P010 7DQ, UK). Both of these publications cite examples of a melt or a solution blending process for the PEI and polyester components. However, they do not describe nor do they suggest the possibility of an xe2x80x9cin-situxe2x80x9d blending process such as is claimed in the present invention. In-situ blending has been applied in previous inventions to the preparation of blends of mostly addition-type polymers, e.g., various polyolefins (U.S. Pat. Nos. 5,225,457; 5,126,398; 5,149,738; 5,047,468; 5,677,375 and 4,522,962) and styrenics (E.P. No. 135,168). The polymers of the present invention, polyesters, are produced by a condensation-type polymerization process, which is fundamentally different from the addition process used for preparing polyolefins and styrenics or from the condensation process of other polymers. The general procedure of the polyester polymerization process is well known to those skilled in the art. Suitable polyesters for this invention are any that are manufactured by a polycondensation process at temperatures greater than the glass transition temperature of the poly(ether imide). Some examples of such polyesters and copolyesters include polycondensation products of diacid (or diester analogs) and glycols such as terephthalic acid, naphthoic acid, 5-sodiosulfoisophthalic acid, isophthalic acid, ethlylene glycol, diethylene glycol, poly(ethylene glycol), poly(propylene glycol), cyclohexane dimethanol, butanediol, neopentyl glycol, trimethylol propane and pentaerythritol. The weight ratio of polyester:poly(ether imide) in the blend is 95:5 to 70:30, preferably 80:20 to 90:10. The poly(ether imide) may be added to a continuous polymerization reactor or a batch polymerization reactor. In one embodiment of the invention the polyester is poly(ethylene-2,6-naphthalate). In another embodiment the poly(ether imide) is a condensation polymer of 2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl] propane dianhydride and m-phenylene diamine. The weight ratio of poly(ethylene-2,6-naphthalate):the condensation polymer of 2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl] propane dianhydride and m-phenylene diamine in the blend is 80:20 to 90:10.
In yet another embodiment, the polyester is poly(ethylene terephthalate). The weight ratio of poly(ethylene terephthalate):poly(ether imide) in the blend is 95:5 to 70:30. A preferred poly(ether imide) is the condensation polymer of 2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl] propane dianhydride and m-phenylene diamine. The weight ratio of poly(ethylene terephthalate):the condensation polymer of 2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl] propane dianhydride and m-phenylene diamine in the blend is 95:5 to 70:30, preferably 80:20 to 90:10.
The method of the invention is useful to prepare a blend for film supports in photographic elements. An exemplary photographic element may comprise a film support bearing at least one photographic layer, the film support comprising a homogenous blend of from 70 to 95 weight percent poly(ethylene naphthalate) and from 30 to 5 weight percent of a poly(ether imide), preferably 80 to 90 weight percent poly(ethylene naphthalate) and from 20 to 10 weight percent of a poly(ether imide).